An experimental new drug may prove a useful alternative to a standard anti-clotting drug, among patients undergoing angioplasty to open up a clogged blood vessel, researchers said Sunday.

Doctors commonly give patients anti-clotting drugs during angioplasty procedures, in which balloons are used to unclog blood vessels, which are then propped up with wire mesh.

One of the most common anti-clotting drugs, clopidogrel, or Plavix, prevents blood cells called platelets from sticking together and creating a clot that can block blood vessels.

In a study of 11,145 patients presented Sunday at an American College of Cardiology meeting in San Francisco, researchers found that cangrelor was slightly better at preventing death, heart attacks and re-clogging of the blood vessel. About 5.9% of those taking Plavix experience one of these problems, compared with 4.7% of those taking cangrelor.

The two drugs were about equal in terms of the risk of causing bleeding problems, according to the study, led by Deepak Bhatt, chief of cardiology at VA Boston Healthcare System. About 1.2% of those taking cangrelor developed shortness of breath, a rate that was four times higher than in the Plavix group.

The new drug, given intravenously, has other benefits, says Steven Nissen, chairman of cardiology at the Cleveland Clinic, who wasn't involved in the new study. He notes that Plavix, a pill, takes a while to take effect. Once Plavix kicks in, its effects last for days. Even aspirin, which also thins the blood, remains effective for the entire, 45-day lifespan of a platelet, the type of blood cell involved in clotting.

"The advantage of this drug is that it's ultra short-acting," Nissen says. With cangrelor, "you can dial on and dial off."

Limiting the drug's effect is important, Nissen says, because it helps reduce complications, such as bleeding.

Cangrelor also may help get some patients to surgery faster, he says. Nissen notes that doctors performing angioplasty often discover that a patient needs heart bypass surgery. But because Plavix increases the risk of bleeding for five days, surgeons must wait to operate.

Other cardiologists, such as Cam Patterson, chief of cardiology at the University of North Carolina at Chapel Hill School of Medicine, says the study leaves important questions unanswered.

A better study, he says, would have been to test cangrelor against a newer pill, ticagrelor, marketed by AstraZeneca as Brilinta, which has been shown to prevent more heart attacks than Plavix.